The disclosures of following applications are herein incorporated by reference: Japanese Patent Application No. H11-357374 filed Dec. 16, 1999; and International Application No. PCT/JP00/08924 filed Dec. 15, 2000.
1. Field of the Invention
The present invention relates to a bayonet mount used to fasten a photographic lens, an adapter or the like of a camera such as a single lens reflex camera, an electronic camera, a video camera or the like, which uses interchangeable lenses, to a body.
2. Description of the Related Art
A bayonet mount in the prior art used in a single lens reflex camera or the like is provided with a plurality of tabs projecting out radially from a cylindrical surface both on the side toward the lens and on the side toward the body. By rotating them relative to each other after they are fitted together, the tabs are interlocked, thus fastening the lens to the body.
While a majority of bayonet mounts in the prior art are constituted of metal, the progress achieved in the field of engineering plastics in recent years has enabled production of bayonet mounts through injection molding of a plastic resin.
However, while the metal bayonet mounts in the prior art achieve a high degree of strength, they present a problem in that since the tabs must be formed through a milling process or the like, the production costs are high. While the production costs of plastic bayonet mounts in the prior art, on the other hand, can be kept low, there is a problem in that a plastic bayonet mount failing to achieve a sufficient degree of strength cannot be used in conjunction with lenses or the like with a large dead load since the tabs cannot withstand the load attributable to the weight of the lens and the body.
There is another problem in that as the plastic bayonet mount in the prior art is mounted and dismounted repeatedly, its durability is reduced.
In order to address the problem of insufficient strength of the plastic bayonet mount, the mount disclosed in Japanese Laid-Open Patent Publication No. H 3-229230 (U.S. Pat. No. 5,262,899) achieves a higher degree of rigidity by forming a cylindrical portion extending along the optical axis of the mount as an integrated part. However, while this mount may be adopted in practical application as long as new mount standards are set, it cannot be utilized in conformance to the current standards, since it does not have compatibility with existing products.
In addition, Japanese Laid-Open Patent Publication No. H3-231726 discloses a mount having the area surrounding a mount lock groove constituted of a metal member to compensate for the insufficient strength of the mount lock groove. However, this mount merely addresses the insufficient strength of the mount lock groove, and does not provide a solution to the insufficient strength of the bayonet mount tabs.
An object of the present invention is to provide a bayonet mount achieving a sufficient degree of strength that can be produced at low cost and a manufacturing method adopted to manufacture the bayonet mount.
In order to attain the above object, a bayonet mount according to the present invention, comprises: a mount main body constituted of resin; and a metal member that, at least partially, reinforces a bayonet tab portion at the mount main body.
In this bayonet mount, it is preferred that: a plurality of bayonet tab portions are provided along a direction of a circumference of the bayonet main body; and the metal member includes a plurality of tab reinforcements for reinforcing the plurality of bayonet tab portions, the plurality of tab reinforcements being formed as an integrated part. In this case, it is preferred that: the metal member includes a plurality of slip-stop portions facing opposite the plurality of tab reinforcements; and the plurality of tab reinforcements and the plurality of slip-stop portions are formed as an integrated unit. Or, it is preferred that: the metal member includes a slip-stop portion facing opposite the plurality of tab reinforcements; and the slip-stop portion is formed continuously along the direction of the circumference of the mount main body.
Also, in any one of above bayonet mounts, it is preferred that: the metal member includes a cylindrical reinforcement formed along a cylindrical shape of the bayonet mount; the plurality of tab reinforcements project out along a radial direction from a central axis of the cylinder at an end surface of the cylindrical reinforcement; and the cylindrical reinforcement and the plurality of tab reinforcements are formed as an integrated unit.
A method according to the present invention for manufacturing a bayonet mount by insert-molding a metal member having a cylindrical reinforcement formed along a cylindrical shape of the bayonet mount and at least one tab reinforcement projecting out along a radial direction from a central axis of the cylindrical shape at an end surface of the cylindrical reinforcement, the cylindrical reinforcement and the tab reinforcement being formed as an integrated unit, comprises: a step in which a position of the metal member relative to a die is regulated by using the cylindrical reinforcement and the tab reinforcement of the metal member; and a step in which a resin is injected after the position of the metal member relative to the die is regulated.
Another method according to the present invention for manufacturing a bayonet mount by insert-molding a metal member having a cylindrical reinforcement formed along a cylindrical shape of the bayonet mount and at least one tab reinforcement projecting out along a radial direction from a central axis of the cylindrical shape at an end surface of the cylindrical reinforcement, the cylindrical reinforcement and the tab reinforcement being formed as an integrated unit, comprises: a radial-direction regulating step in which a position of the metal member relative to a die along a radial direction of the cylindrical shape is regulated by using the cylindrical reinforcement of the metal member; a rotational-direction regulating step in which the position of the metal member relative to the die along a rotational direction around a central axis of the cylindrical shape is regulated by using the tab reinforcement of the metal member; an axial-direction regulating step in which the position of the metal member relative to the die along a direction of the central axis of the cylindrical shape is regulated by using the tab reinforcement of the metal member; and an injecting step in which a resin is injected after the position of the metal member relative to the die is regulated along the radial direction, the rotational direction and the direction of the central axis.
In this method for manufacturing a bayonet mount, it is preferred that the radial-direction regulating step and the axial-direction regulating step are implemented concurrently by using a single member provided at the die.
Also, it is preferred that a bayonet mount according to the present invention is manufactured through the above method for manufacturing a bayonet mount.
Thus, a bayonet mount achieving a high degree of strength at the bayonet tabs can be manufactured with ease at low production cost, as described above. Furthermore, the position of the metal member relative to the mount main body can be set with more ease and with a higher degree of accuracy.